Lightroom: Sometimes Backup takes forever

My catalog is parametered for chack/backup/optimize at each exit.
Due to relatively frquent crashes of LR4 and the load I currently do, My catalog is backup between 3 and 8 times a day (Until now, I've always restarted LR without needing the backup).

But at least 2 times, I've had to stop the backup (with the windows command) because it didn't progress (the message window was fashing and the progress rule came back to 5% every 30 sec or so).

My current cataloog is 870MB large, with more than 1.14 tera of photo files on an external sata disk.